WATER, MEGACITIES AND GLOBAL CHANGE - UNESCO
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Online Pre-Conference WATER, MEGACITIES AND GLOBAL CHANGE 7 – 11 December 2020 Holistic Water Management 8 December 2020 Water quality in Saigon River (Vietnam): modelling scenarios by C-GEM A.T Nguyen, J. Némery, N. Gratiot, T.S Dao, V. Thieu, J. Garnier and G. Laruelle
Transcript of WATER, MEGACITIES AND GLOBAL CHANGE - UNESCO
Online Pre-Conference
WATER, MEGACITIES AND GLOBAL CHANGE
7 – 11 December 2020
Holistic Water Management8 December 2020
Water quality in Saigon River (Vietnam):modelling scenarios by C-GEMA.T Nguyen, J. Némery, N. Gratiot, T.S Dao, V. Thieu,J. Garnier and G. Laruelle
PRE-CONFERENCE “WATER, MEGACITIES AND GLOBAL CHANGE”
Summary
1. Introduction of Ho Chi Minh City and Saigon River 2. Objectives3. Implementation of C-GEM model4. Three scenarios of WWTPs construction5. Conclusion and perspectives
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1. Introduction: Distribution of megacities
https://sedac.ciesin.columbia.edu
Estuarine and coastal areas 67% of the megacities (Glasow et al., 2013)
Vietnam
Global Population Density 201519
Ho Chi Minh City (Southern Vietnam)1. Introduction
Ho Chi Minh City (HCMC):• Economic capital of VN• 9M inhabitant, 3.4%/yr
(GSO Vietnam, 2019)
Water issues in HCMC:• Water pollution in urban canals• Lacking wastewater treatment
plants (WWTPs) 80% WWs into canals, rivers(Nguyen et al., 2020)
©Vietnamnet 2019
05/2015, Nhieu Loc canal 04/2019, Tham Luong canal20
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Saigon River System1. Introduction
Saigon River:• Tropical estuary (dry and wet season)• Tidal regime from East Sea Vietnam• Connects to urban canals, Dongnai River
Water quality in Saigon River:
• Urban section
• NH4 (1.5mg/L), TOC (10 mg/L)
• O2 (<1.5 mg/L), high Chl-a (100
ug/L)
High risk of eutrophication in Saigon
River
(Nguyen et al, 2019)New WWTPs for safety of water resources
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Water production(90% river water, 2019)
Dau Tieng Reservoir
Tri AnReservoir Q=~30m3/s
Q=~300m3/s
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2. Objectives
Based on WWTP construction plan (decision n°24/QĐ‐TTg approved by Prime Minister, 2010) Three scenarios 2015, 2025 and 2050 Using the estuarine biogeochemical model (C-GEM)
2015
2025
2050
8M
11M
23M
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Saigon River
Urban canalsInstallation cost: 2.3 billion USD for 12 WWTPs (2.8M m3/d)(900 USD for 1 m3 wastewater)
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3. C-GEM model
Carbon-Generic Estuary Model (C-GEM) 1D, reactive-transport model
Applying C-GEM for Saigon River in dry season23
Volta et al., 2016
Vietnam Center For monitoring
Monthly
Upstream Q
Tidal force
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3. Model validationHydrodynamics and transport module
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saltwater intrusion
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3. Model validationSimulation vs observation in dry season Saigon River
Model performance:- Coefficient correlations: (0.6 to 0.9)- Percentage bias: <20% (except PO4)
Nguyen et al. in prep,
STOTEN
Biogeochemical processes
Nitrification is the main factor of DO depletion in Saigon River 25
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3. Model results
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Displacement of pollutant cloud/tidal cycles
• 30 km of pollutant cloud• Movement in 10 km
30 km
10 km
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4. Scenarios
Based on HCMC’s development plan
Keep the same forcings+ climate change effect in 2050
Calculation of lateral inputs
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4. Scenarios
2015 2025 2050
DO
NH4
TOC
PO4
• 2025: improvement in water quality
• 2050: return to bad condition 12 WWTPs will not be enough
for 23M inhabitants in 2050 NH4 always high in 3 scenarios
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Water quality in Saigon River in three scenarios
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ConclusionsKey findings based on C-GEM simulation:1. Impact of urban discharge to water quality in Saigon River2. Main process to hypoxia in urban section: nitrification (high NH4)3. 12 WWTPs in 2050 will not be enoughSuggested solutions:1. Improving NH4 treatment capacity of WWTPs 2. Alternative urban wastewater management (Nature-based Solutions - NBS)
Illustration by Masi et al 2018 29
NBS
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WATER, MEGACITIES AND GLOBAL CHANGE
7 – 11 December 2020
Thank you for your attention !
Nguyen Truong [email protected]
